ZL1 Chevelle Intake Swap - Six Shooter Shoot Out

We Put Barry Grant's Big Block 3x2 Setup To The Test On A Odern Zl-1.

Multiple inline carburetor setups date back decades, but gained mythical status in the heyday of the musclecar. In the Mopar world it was a "Six Pack" and Pontiac guys had "Tri-Power," but there was never really a catchy (or affectionate) name for Chevy's 348 W-motors or the '67-69 big-block engines equipped with three two-barrel carburetors. An air cleaner decal with a "3x2" designation was pretty much it. If it wasn't running properly, people cursed them as "Triple Trouble."

Truth was the trips generally looked better than they performed. Tuning was tricky and the vacuum-operated linkages used on the 427s Vettes often made for sloppy performance. Indeed, most engine builders discourage the use of these systems for those who want maximum performance, as a well-tuned four-barrel will out-perform them on the dyno and at the track.

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The subject of our story is this slick '71 Chevelle owned by Chris Price. Inside is a Spartan bench-seat cabin. The exterior lacks SS trim and is festooned with seemingly stock steel wheels and dog-dish caps-but they're really custom-tooled 16-inch wheels with billet GM-style COPO dog-dish hubcaps-Chris probably has more into these caps than the whole engine! Under the hood is a ZL-1 engine.

Still, there's an undeniable "wow" factor that comes with a trio of inline carburetors. It looks exotic. It looks "musclecar." For some, that's all the reason they need. Carb wizard Barry Grant, however, has revisited the 3x2 idea with an eye toward serious performance, not just cruise-night credibility. To that end, his company designed the Six Shooter line of manifold and carburetor systems. And while versions for Pontiac engines and Chevy small-blocks have been out for a little while now, the big-block versions have just recently hit the market.

Actually, there are two versions for the big-block Six Shooter: one for rectangular-port heads and one for oval-port heads. Thinking such a setup would enhance the underhood appeal and, with luck, the rear-wheel output of his ZL-1-powered Chevelle, Michigan-based engine builder Chris Price elected to give the big-block Six Shooter a whirl. The car is a subtle, look-at-it-twice resto-mod that's powered by the same long-block GM Performance Parts used for the limited-run Ramjet ZL-1. To say the Chevelle is a slick piece would do a huge injustice to the word slick.

We tagged along and met Price and a few of his buddies from Retrotek Kustoms, of Howell, Michigan, at Flint's Hardcore Racing, where the intake swap and before/after chassis dyno tests would take place. Frankly, we were skeptical that the Six Shooter would make a substantial gain when compared with the engine's four-barrel induction system. "Three horsepower," we guessed-an educated guess based on years of experience testing bolt-on performance items.

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Prior to initial dyno testing and the intake swap, the ZL-1 engine's timing was double-checked, as the reference point for the Six Shooter system.

The car was baselined on Hardcore's chassis dyno, where it made 343 hp and 348 lb-ft of torque at the rear wheels. It was a respectable baseline number, but to be honest we expected a little more from the 427 engine. After the baseline numbers were recorded, the manifold swap commenced.

We were generally pleased with the Six Shooter kit, which included the intake manifold, trio of polished Demon carbs, carb linkage, and an air cleaner. However, there were some details that puzzled us. The water neck on the manifold pointed straight ahead, whereas Chevy manifolds typically have angled necks. This design feature necessitated some creative hose cutting to make a workable upper radiator hose. Also, a boss and tapped hole had to be cut in to the front of the manifold to accommodate an electric fan temperature sending unit. This is a common feature on other aftermarket intakes and we'd wished Barry Grant had added it to its own when it tooled-up for the Six Shooter.

We also ran into some manifold-to-cylinder-head fitment issues. Slightly askew bolt-hole alignment meant some trial-and-error grinding to elongate the manifold's bolt holes in order to produce a smooth, snag-free run-down of the fasteners into the cylinder heads. The manifold used for our story was an early production piece, so there might still have been a few bugs to work out on the production line. In fact, we brought this to the attention of Barry Grant and we feel confident the issue has been addressed.

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ZL1 Chevelle Intake Swap - Six Shooter Shoot Out

The subject of our story is this slick '71 Chevelle owned by Chris Price. Inside is a Spartan bench-seat cabin. The exterior lacks SS trim and is festooned with seemingly stock steel wheels and dog-dish caps-but they're really custom-tooled 16-inch wheels with billet GM-style COPO dog-dish hubcaps-Chris probably has more into these caps than the whole engine! Under the hood is a ZL-1 engine.

Prior to initial dyno testing and the intake swap, the ZL-1 engine's timing was double-checked, as the reference point for the Six Shooter system.

Hardcore Racing was the site for our dyno testing and intake swap. On the chassis dyno, the "stock" ZL-1, with its single-four setup, laid down 343 rear-wheel horses and 358 lb-ft of torque.

This is the Six Shooter setup pretty much as it's delivered. It includes the intake manifold with the carburetors and linkage pre-installed. The kit also includes the air cleaner, which looks a little too "street rod" for our subtle musclecar. Finding (or crafting) a '67-69-style Corvette 3x2 air cleaner would better suit the car.

Aspiration with the Six Shooter system comes via three 250-cfm Demon two-barrel carburetors. The center carb has an electric choke. At light-throttle/highway cruising speeds, the system breathes only through the center carb. A progressive throttle linkage kicks in the other carbs as needed.

One of the Six Shooter's details we weren't thrilled with was the straight-ahead position of the water neck-standard Chevy intakes are canted toward the driver side. While this may work fine and look symmetrical on totally custom applications, such as street rods, it presents a radiator hose fitment issue with stock-type underhood setups, such as our Chevelle. The design forced us to throw out the car's stock hose and cut-to-fit a generic hose. We'd much prefer the standard canted neck, or an option to choose the neck.

The swap procedure began with the disassembly of the four-barrel equipment. This meant first disconnecting the spark plug wires and pulling off the distributor cap.

The engine's MSD distributor was clearly marked and its position carefully noted, in hope that timing would be close to accurate when the new intake was installed. This was particularly important, as the common trick of marking both the manifold and distributor wouldn't work, because the old manifold would be replaced with the Six Shooter.

With the distributor removed, and the fuel lines and temperature sensors disconnected, the four-barrel setup was lifted up and out of the engine compartment.

With the old intake out of the way, the block's valley and head ports were blocked off so that gasket and sealer residue could be scraped off. Note the use of paper towels rather than cloth rags; rags have fibers and threads that can fall into the engine. Paper towels are safer.

Next, the old intake's sensors were transferred to the Six Shooter intake. The Six Shooter manifold was drilled and tapped to accommodate an electric fan temperature sending unit.

New intake manifold gaskets were carefully set in place; as it was just about time to lower the new intake into place.

Finally, the Six Shooter dropped into place without a hang-up and the attaching hardware torqued down without a snag. Pretty sexy looking valvetrain, too, huh?

In order to ensure a proper, snag-free run-down of the manifold's hardware, some of the manifold's bolt holes were manipulated with a grinder. It was a trial-and-error process that required several attempts before the correct positions were found. We believe we can chalk this up to having a very early production unit.

A new fuel line from the fuel pump to the carbs was required. Car owner Chris Price fabbed up this custom-bent hard line for the job.

With the carbs installed on the manifold, work moved quickly to the throttle linkage connection. A longer length of throttle cable was required, when compared with the four-barrel setup. This was attained disassembling the cable, shortening the cable housing, and re-installing the cable assembly into the bracket.

There was more tinkering when it came to determining the proper setting for the carbs' linkage, so that all three carbs would go to wide-open when the throttle was fully extended.

With the Six Shooter system in place and apparently in sync, linkage-wise, the rest of the details were buttoned up, including reinstalling the distributor, adding coolant, etc.

Here's the finished installation, minus the kit's polished air cleaner. The triple-carb appearance definitely harkens back to the musclecar era and provides some underhood flash when compared to garden-variety four-barrel systems. We were thrilled, too, to find out it delivered greater performance and not just an interesting look.

Back on the chassis dyno, operated by Hardcore Racing's Keith Benson, the ZL-1-powered Chevelle picked up 15 hp and 28 lb-ft of torque at the rear wheels, for a bestof 358 horses and 376 lb-ft.